Poxviruses differ from other viruses in their size and complexity. They are large, with linear, double stranded DNA encoding for about 200 proteins and is the only known DNA virus that replicates entirely in the cytoplasm1. They are reported in both invertebrates (Entomopoxvirinae) and vertebrates (Chordopoxvirinae). Poxvirus infections, in general, are acute, with no strong evidence for latent, persistent, or chronic infections2. Variola virus, the causative agent of smallpox, belongs to this group of virus. The vaccinia virus used to prevent smallpox. The narrow host specificity of Variola virus was important in the eradication of smallpox3.
Hence, some members of the Poxviridae can cause severe, systemic disease, while others, can cause mild, localized disease depending on the virus species, the route of entry, the host species and its immune status4 The host tropism varies from narrow to broad5 and the virus is epitheliotrophic, typically causing proliferation of epithelial cells6.
In general, little is known about poxvirus infections in aquatic animals7-10.